1. Field of the Invention
The present invention relates to a charging apparatus, a print engine that incorporates the charging apparatus, and an image forming apparatus that incorporates the print engine. An image bearing body is charged to a desired potential and is then irradiated with light to form an electrostatic latent image on the image bearing body. The electrostatic latent image is developed with a developer material into a visible image. Such image forming apparatuses include copying machines, printers, and facsimile machines.
2. Description of the Related Art
Among conventional charging apparatuses that charge a photoconductive body is one in which a charging film member has one end portion fixed to an apparatus body and another end portion in pressure contact with a photoconductive body by the use of the spring action or resiliency of the film. A voltage is applied to the charging film, which in turn charges the surface of the photoconductive body.
A high speed image forming apparatus uses a low-melting point toner. Low-melting point toner is apt to adhere to surrounding structural members. In order to prevent adhesion of the low-melting point toner to the surroundings, a large amount of external additive such as silica is added to the toner. The external additive and toner that have failed to be transferred onto a recording medium during transferring remain on the photoconductive body. As the photoconductive body continues to rotate, the external additive and toner are carried to a charging member disposed downstream of the transfer point. Even if the resiliency of the charging film is controlled in a conventional manner, it is still difficult to prevent the external additive from being trapped in gaps between the charging film and the photoconductor. This causes variations in the electrical discharge that takes place between the charging film and the photoconductive body, resulting in poor charging performance of the photoconductive body. Poor charging performance may result in white streaks on a printed image, impairing print quality of the image.